The present invention relates generally to hydraulic control for an automatic transmission, and more particularly, to lubrication control of a start clutch of a V-belt type continuously variable transmission (CVT).
As described in Service Manual for Fit, Book Structure, 4–18 Honda Multimatic Transmission, published by Honda Motor Co., Ltd. on June, 2001, a wet start clutch typically adopts a shaft-center lubrication method wherein an output shaft with a hollow portion serves as a lubrication passage to ensure lubrication of the clutch. Hydraulic oil discharged from a pump is used as lubricating oil to be supplied to the clutch.
With the above lubrication method, however, the output shaft is not rotated when the vehicle is at a standstill, producing no centrifugal hydraulic pressure. Then, supplied lubricating oil is not discharged smoothly, resulting in greater drag torque due to occurrence of agitation of lubricating oil at the clutch. When carrying out neutral-drive (N-D) select at a very low temperature, particularly, drag torque is further greater due to greater viscosity of lubricating oil, reducing the engine speed, leading to possible occurrence of engine stop.